The effect of preoperative oral carbohydrate intake on perioperative well-being in patients undergoing hip and lower extremity orthopedic surgery under spinal anesthesia: a randomized controlled trial

Abstract

Background

The administration of preoperative oral carbohydrate (POC) has been shown to enhance patient well-being and expedite postoperative recovery. Nevertheless, evidence regarding its efficacy in orthopedic patients remains insufficient and warrants further investigation. This study aimed to address gaps by evaluating the effect of preoperative oral dextrose (POD) intake on perioperative well-being parameters (including thirst, hunger, anxiety, pain, nausea, and vomiting) in patients undergoing hip and lower extremity surgeries with spinal anesthesia.

Methods

In this randomized controlled trial, 70 adult patients scheduled for orthopedic surgery were assigned to either the dextrose (POD intake) group or the fasting group (routine fasting periods of 8–10 h). Perioperative subjective well-being, including measures of thirst, hunger, anxiety, pain, nausea, and vomiting, was evaluated using the Visual Analogue Scale (VAS) both preoperatively and at multiple postoperative time points (T0, T6h, and T24h). Adverse postoperative events were monitored for 24 h following surgery.

Results

Significant improvements in perioperative thirst and pain scores were observed in the dextrose group compared to the fasting group (p = 0.041 and p = 0.003, respectively). The dextrose group consistently reported lower VAS scores for thirst, hunger, pain, and anxiety across all time points (T0, T6h, T24h) (p < 0.001). No significant differences were found between groups for nausea or vomiting (p > 0.05).

Conclusion

The administration of preoperative oral carbohydrate (POC) showed no clinically significant impact on perioperative nausea or vomiting in orthopedic patients. However, it significantly improved other perioperative well-being parameters such as thirst, hunger, anxiety, and pain, highlighting its potential to enhance patient comfort and recovery outcomes.

Trial registration

Iranian Registry of Clinical Trials, IRCT20191017045139N2. Registered on 28 January 2024.

Introduction

Surgical interventions trigger a cascade of catabolic responses characterized by the release of stress hormones, such as cortisol, along with the activation of pro-inflammatory pathways. These responses contribute to the development of insulin resistance (IR) and metabolic disturbances [1–4] (Fig. 1).

Fig. 1.

Preoperative stressors plus hormonal response to surgical stress [1, 2, 4, 12, 47, 59, 65, 66]. HPA: hypothalamic–pituitary–adrenal axis; SAM: sympathetic-adrenomedullary system; CRH: Corticotropin-Releasing Hormone; ACTH: Adrenocorticotropic Hormone; IL1β: Interleukin 1 beta; IL6: Interleukin 6; IL8: Interleukin 8; TNFα: Tumor Necrosis Factor α; CRP: C-Reactive Protein; PI3K: Phosphoinositide 3-kinase; GLUT4: Glucose Transporter Type 4

Prolonged preoperative fasting heightens metabolic stress [5, 6], by raising glucocorticoid and glucagon levels and lowering insulin sensitivity [1, 2, 7]. It also disrupts glucose metabolism, leading to complications such as confusion, discomfort, headache, and electrolyte imbalance [5, 8].

Addressing these metabolic disruptions and perioperative discomforts, including dehydration, anxiety, thirst, hunger, dry mouth, postoperative nausea and vomiting (PONV) [9–11] are essential for enhancing postoperative recovery and overall quality of life [8].

Orthopedic patients face unique perioperative challenges, including the physiological stress associated with surgery, pain, and the risks inherent to spinal anesthesia (SA) [5, 8]. Malnutrition in orthopedic patients, especially those with hip fractures, exacerbates the catabolic effects of surgical stress, leading to insulin resistance, muscle loss, and impaired recovery. Given the negative impact of prolonged fasting on the metabolic state [3, 12], revised fasting guidelines have endorsed the consumption of clear liquids up to 2–3 h before surgery [13, 14].

The Enhanced Recovery After Surgery (ERAS) program is a strategic approach designed to mitigate metabolic disturbances and improve patient comfort during the perioperative period [4, 12]. ERAS protocols recommend preoperative oral carbohydrate (POC) intake to mitigate surgical stress and counteract the adverse fasting effects [3]. POC intake enhances insulin sensitivity, immune response, and reduces postoperative metabolic complications [3, 6, 10, 15] (Fig. 2). Additionally, it alleviates perioperative discomforts, such as thirst, hunger, dry mouth, fatigue, anxiety, nausea, and vomiting, thereby enhancing sleep quality, energy and patient satisfaction [16–20].

Fig. 2.

Mechanisms behind the effects of Preoperative Oral Carbohydrate (POC) intake as part of the ERAS protocol in enhancing patient comfort or well-being [3, 5, 19, 26, 67]

Despite a significant body of evidence supporting POC intake, there remain notable inconsistencies and gaps in the implementation and adherence to this strategy across different healthcare settings [3, 5, 19]. While systematic reviews and meta-analyses report reductions in IR, its effect on overall patient well-being remains inconclusive [21]. For example, Doo et al. found no improvements in patient satisfaction or well-being following thyroidectomy [6]. Similarly, studies involving laparoscopic cholecystectomy and lumbar disc surgery reported no significant differences in perioperative pain, nausea, vomiting, or fatigue between fasting and carbohydrate groups [22, 23]. Sada et al. observed no significant effect on overall well-being, despite reductions in postoperative thirst in colorectal surgery patients [18].

While POC intake is well-supported across multiple surgical specialties [24], its specific role in orthopedic procedures, particularly hip and lower extremity surgeries, remains unclear and underexplored [25].

The ERAS guidelines currently refrain from recommending POC intake for these surgeries due to limited data on both immediate and long-term postoperative outcomes [25]. For instance, While Ertural et al. demonstrated reductions in anxiety, pain, thirst, hunger, and nausea in hip arthroplasty (HA) patients under SA [26], other studies have indicated no significant improvement in patient well-being following POC intake in those undergoing total knee arthroplasty (TKA) or hip procedures under epidural or SA [27–29].

Additionally, Kweon et al. [10] reported that POC intake in patients undergoing cephalomedullary nailing for proximal femur fractures under SA failed to relieve anxiety, nausea, or vomiting.

These inconsistencies in POC intake highlight the need for further investigation in hip and lower extremity orthopedic procedures using SA, given that orthopedic patients face unique perioperative challenges, including the significant physiological stress of surgery [29], and that ERAS protocols advocate for SA to reduce opioid use, provide reliable analgesia, cause little disturbance to hemodynamics [30, 31] and have a positive postoperative outcome over general anesthesia [32].

Despite these challenges, optimizing postoperative recovery and patient well-being remains a key priority in orthopedic surgery [8]. Nonetheless, the lack of robust evidence supporting POC intake underscores the need for further research in this area [25].

This study aims to address gaps by evaluating the effect of preoperative oral dextrose (POD) intake on perioperative well-being parameters (including thirst, hunger, anxiety, pain, nausea, and vomiting) in patients undergoing hip and lower extremity surgeries with spinal anesthesia. We hypothesize that POD intake will significantly improve subjective well-being parameters compared to standard fasting in this population. Through this investigation, the study aims to optimize perioperative well-being and contribute to the advancement of orthopedic surgical care.

Methods

Study design

This single-blind, randomized controlled clinical trial was conducted between January and August 2024 at two hospitals in Kashan, Iran, involving eligible participants.

Participants

The sample size was calculated based on mean VAS pain scores (6.1 ± 2.1 and 4.8 ± 1.8) from a previous study [5]. With 80% power and a 95% confidence level, a minimum of 35 participants per group was required (Formula 1). The online-generated block randomization (1:1 ratio) with a fixed block size of four was performed. Allocation concealment was ensured using sealed, opaque envelopes prepared by an independent epidemiologist and opened by the investigator (first author) only at the time of intervention. Data analysis was performed by a statistician who was blinded to group allocation, with assignments coded as A (dextrose group) and B (fasting group). However, the investigator responsible for recording VAS scores was not blinded. Moreover, due to the nature of the intervention, patients knew their group assignment (dextrose or fasting).

1

The inclusion criteria included: adult patients (≥ 18 years), consent to participate in this study, scheduled for elective orthopedic surgeries of the hip or lower extremities under SA, surgery duration of at least two hours, effective comprehension and communication skills, and classification as American Society of Anesthesiologists (ASA) physical status class I or II.

Exclusion criteria included participant withdrawal, conversion to general anesthesia due to inadequate SA, a delay of over three hours between dextrose intake and transfer to the OR, or intake less than two hours before anesthesia (Patients who consumed dextrose less than 120 min before anesthesia were excluded due to aspiration risk, in line with ERAS guidelines on 90-minute gastric emptying for clear fluids). Additional exclusions were intraoperative blood transfusion, surgery cancellation, perioperative mortality, and a history of conditions such as uncontrolled hypertension, motion sickness, gastroparesis, gastroesophageal reflux disease(GERD), esophageal disorders (strictures, achalasia), severe systemic diseases (brain, heart, lungs, liver, kidneys), morbid obesity (BMI > 40 kg/m²), metabolic or endocrine disorders, pathological fractures, or suspected musculoskeletal issues.

Intervention

In the afternoon of the day before surgery, patients who had been referred to the surgical units for hip or lower extremities surgery provided their consent, and the first author randomly allocated them into either the fasting group (n = 35) or the dextrose group (n = 35). All participants adhered to the study protocol (Fig. 3).

Fig. 3.

CONSORT flow diagram

All patients in both groups received 1,000 mL of a 0.3% NaCl in 3.33% dextrose solution after the NPO period commenced at 10:00 p.m. This routine care was undertaken to maintain an adequate effective circulating volume, preserve normal electrolyte balance, and meet the metabolic demands during fasting. The fluid volume was calculated according to the Holliday and Segar formula [33], which allocates 100 mL for the first 10 kg of body mass, a method applied to both adult and pediatric patients. Moreover, as part of routine care, all patients received intravenous Ringer’s solution was started at 10 mL/kg/h 30 min before spinal anesthesia and continued at 2 mL/kg/h during surgery [34].

Patients in the fasting group adhered to standard preoperative fasting guidelines, refraining from solids and liquids after 10:00 p.m. The dextrose group also fasted from solids after 10:00 p.m. These patients received 200 mL of 10% oral dextrose solution (10 g glucose/100 mL, osmolality: 555.2 mOsm/L, delivering 34 kcal/100 mL) 2–3 h before surgery (approximately 6:00–6:30 a.m.). Patients were instructed to consume the entire dextrose solution gradually over 30–60 min. No additional clear fluids were permitted.

Adherence to the dextrose intervention was monitored by the investigator (first author) who directly observed patients consuming the solution and recorded the volume ingested.

While ERAS protocols often recommend complex carbohydrates like 12.5% maltodextrin, we selected 10% dextrose due to its availability, lower cost, and institutional policy limitations [35].

Perioperative management

On arrival in the OR, all patients underwent monitoring with noninvasive blood pressure (NIBP), electrocardiogram (ECG), pulse oximeter for assessing O2 saturation (SaO2), heart rate (HR), and axillary body temperature measurements. Body temperature was maintained between 36 °C and 37 °C, while the OR temperature was kept between 22 °C and 25 °C. No prophylactic antiemetics (e.g., ondansetron) were administered. However, if ondansetron was required postoperatively based on the anesthesiologist’s clinical judgment, all administered doses were recorded during data collection.

An experienced anesthesiologist performed spinal anesthesia (SA) in the sitting position using a 25–27-gauge spinal Quincke-tip needle (EXEL INT International Company) at the L3-L4 or L4-L5 interspace. After confirming cerebrospinal fluid flow, a standard dose of 12–20 mg of hyperbaric bupivacaine 0.5% was injected into the subarachnoid space based on the required level of anesthesia, and patients were positioned supine [34].

Subsequently, 50 to 100 micrograms of fentanyl and 1 to 2 milligrams of midazolam were administered to all patients, with dosages determined based on weight, time of surgery, and clinical judgment [34, 36]. The surgeon, based on the clinical diagnosis or fracture location, selected the surgical approach and type of implant or prosthesis.

Intraoperatively, patients received supplemental oxygen (5 L/min via facial mask). Postoperatively, Ringer’s infusion rate was maintained at 2 mL/kg/h to account for intraoperative losses such as blood loss and fluid redistribution [34, 36].

All patients received routine care in the post-anesthesia care unit (PACU), including temperature management with blankets. NIBP, HR, SaO2, and ECG of the patients were regularly monitored and recorded every five minutes, and temperature was measured every 10 min. The PACU temperature ranged from 25 °C to 27 °C during the study.

Measurement

• (A)Demographic and Clinical Information Questionnaire that included age, gender, education, marital status, type of surgery, type of implant used, pathological site (unilateral or bilateral), Body Mass Index (BMI), duration of anesthesia, duration of surgery and blood loss during surgery.
• (B)Subjective well-being was assessed using numerical Visual Analogue Scale (VAS) scores [9, 16, 26, 28] for six parameters: thirst, hunger, anxiety, pain, nausea, and vomiting. Each was rated on a scale from 0 (none) to 10 (severe). Specifically, thirst, hunger, and anxiety were rated from 0 (no thirst/hunger/anxiety) to 10 (extreme thirst/hunger/anxiety), while pain, nausea, and vomiting followed the same 0–10 scale for severity. Assessments were performed at three time points: 30 min before spinal anesthesia (T0), six hours postoperatively (T6h), and 24 h postoperatively (T24h).

Data analysis

Data analysis was performed using IBM SPSS Statistics, version 27.0 (IBM Corp., Chicago, IL). Descriptive statistics were presented as means and standard deviations for quantitative variables and as frequencies and percentages for categorical variables. The normality of quantitative data was assessed using skewness and kurtosis indices. Skewness values within ± 2 and kurtosis values within ± 5 were considered indicative of a normal distribution. Chi-square or Fisher’s exact test, and two-tailed Student’s t-tests were used to compare the patients’ categorical and quantitative demographic and clinical characteristics, respectively. Repeated measures analysis of variance (ANOVA) assessed changes in mean VAS scores within and between groups across the three time points. Mauchly’s test was applied to assess sphericity (P > 0.05). If sphericity was violated (P < 0.05), the Greenhouse–Geisser correction was employed. In addition, the Bonferroni post hoc test was used for pairwise comparisons. P < 0.05 was considered statistically significant.

Ethical considerations

Ethical approval was obtained from the Kashan University of Medical Sciences Ethics Committee under the code of IR.KAUMS.NUHEPM.REC.1402.071. This study was registered in the Iranian clinical trial registration system under the number IRCT20191017045139N2. The information and objectives of the study were provided to all participants, and they were assured that their information would remain confidential. Furthermore, all participants signed an informed consent form. The study also adhered to the Consolidated Standards of Reporting Trials (CONSORT) guidelines [37].

Results

Demographic and clinical information

The mean age of all patients was 63 ± 19.45 years, and their age range was 19–91 years. Moreover, the mean BMI of all patients was 26.89 ± 4.95 (kg/m²), and the BMI range was between 17.30 and 47.75 (kg/m²). In addition, the mean duration of surgery for all patients was 127.64 ± 25.94 min, with a range of 120 to 190 min. The mean duration of anesthesia for all patients was 156.64 ± 26.13 min with a range of 135 to 210 min. All patients had unilateral pathologies or injuries. Furthermore, no patients experienced severe nausea or vomiting during the initial 24-hour postoperative period, thereby eliminating the necessity for antiemetic therapy.

As shown in Table 1, the results of the Chi-square test and Fisher’s exact test did not show a significant difference between the two groups in terms of qualitative demographic and clinical characteristics (P ≥ 0.05). Independent t-test also showed that there was no statistically significant difference between the two groups in terms of quantitative variables (P ≥ 0.05).

Table 1.

Baseline demographic and clinical characteristics

Characteristics		Groups
		Fasting (N = 35)	Dextrose (N = 35)	P value
Gender, N (%)	Female	22 (62.9%)	14 (40%)	0.56a
	Male	13 (37.1%)	21 (60%)
Marital status, N (%)	Single	6 (42.9%)	8 (57.1%)	0.76b
	Married	43 (50.6%)	42 (49.4%)
	Widowed	2 (66.7%)	1 (33.3%)
	Divorced	1 (2.9%)	0 (0.0%)
Education level, N (%)	Illiterate	10 (28.6%)	13 (37.1%)	0.45b
	Junior school	16 (45.7%)	14 (40.0%)
	High school	9 (25.7%)	6 (17.1%)
	University	0 (0.0%)	2 (5.7%)
Clinical diagnosis	Hip Fracture	3 (8.6%)	2 (5.7%)	0.17b
	Hip Osteoarthritis	5 (14.3%)	1 (2.9%)
	Femoral Neck Fracture	8 (22.9%)	8 (22.9%)
	Subtrochanteric Fracture	4 (11.4)	6 (17.1)
	Femoral Shaft Fracture	7 (20%)	14 (40%)
	Knee Osteoarthritis	5 (14.3%)	7 (20.0%)
	Tibia Fracture	4 (11.4%)	1 (2.9%)
Type of surgery, N (%)	ORIF	24 (68.6%)	24 (68.6%)	0.29b
	THA	4 (11.4%)	3 (8.6%)
	TBA	2 (5.7%)	7 (20%)
	TKA	5 (14.3%)	1 (2.9%)
Type of implant, N (%)	Hip Prosthesis	4 (11.4%)	3 (8.6%)	0.22b
	Bipolar Prosthesis	2 (5.7%)	7 (20%)
	Dynamic Hip Screw	6 (17.1%)	1 (2.9%)
	Gamma Nail	4 (11.4%)	6 (17.1%)
	Intramedullary Nail	2 (5.7%)	1 (2.9%)
	Knee Prosthesis	5 (14.3%)	1 (2.9%)
	Screw and Plate	12 (34.3%)	16 (45.7%)
Age (years), mean ± SD		64.74 ± 18.36	61.26 ± 20.6	0.45c
Body Mass Index (kg/m²), mean ± SD		27.11 ± 5.27	26.67 ± 4.66	0.70c
Duration of Anesthesia (minutes), mean ± SD		163.31 ± 22.00	157.57 ± 20.77	0.26c
Duration of Surgery (minutes), mean ± SD		136.29 ± 19.86	132.46 ± 17.17	0.39c
Blood Loss During Surgery (milliliters), mean ± SD		725.43 ± 188.88	658.29 ± 184.41	0.13c

TKA Total Hip Arthroplasty, TBA Hip Bipolar Arthroplasty, TKA Total Knee Arthroplasty, ORIF Open Reduction and Internal Fixation

^aChi-Square test; ^bFisher’s Exact Test; ^cIndependent T-test

Perioperative patient well-being

Thirst Visual Analogue Scale Score (TVASS)

A significant time-by-group interaction observed for TVASS (F = 3.38, p = 0.041), with greater improvements in the dextrose group at all time points (p < 0.001). Both groups showed time-related reductions (p < 0.001), though in the fasting group, no significant difference was noted between T0 and T24h (p = 1.00) (Table 2; Fig. 4).

Table 2.

Within- and between-group comparisons of the mean TVASSs and HVASSs at three time points

Outcomes			Groups		Between-group comparisonsb
			Fasting (n = 35) mean ± SD	Dextrose (n = 35) mean ± SD
TVASS (0–10)	T0		6.0 ± 2.67	3.23 ± 2.56	˂0.001
	T6h		8.37 ± 1.89	4.31 ± 2.32	˂0.001
	T24h		5.89 ± 2.41	1.77 ± 1.98	˂0.001
	Within-group comparisons (Effect of time)		F = 31.75 ES = 0.478 p ˂ 0.001	F = 26.13 ES = 0.438 p ˂ 0.001	Time-group interactiona
	Pairwise comparisons c	Difference T0 & T6h	p ˂ 0.001	P = 0.03	Mauchly’s Test	Greenhouse ‒ Geisser
		Difference T0 & T24h	P = 1.00	P = 0.007	χ 2 = 6.65 P = 0.03	F = 3.38 ES = 0.041 P ˂ 0.04
		Difference T6h & T24h	p ˂ 0.001	p ˂ 0.001
HVASS (0–10)	T0		3.71 ± 2.35	1.74 ± 2.21	˂0.001
	T6h		4.63 ± 2.65	2.0 ± 2.27	˂0.001
	T24h		2.40 ± 2.39	0.57 ± 1.35	˂0.001
	Within-group comparisons (Effect of time)		F = 21.09 ES = 0.38 p˂0.001	F = 9.72 ES = 0.22 p˂0.001	Time-group interactiona
	Pairwise comparisonsc	Difference T0 & T6h	P = 0.07	P = 1.00	Mauchly’s Test	Sphericity Assumed
		Difference T0 & T24h	P = 0.002	P = 0.008	χ 2 = 1.65 P = 0.43	F = 1.31 ES = 0.019 P = 0.27
		Difference T6h & T24h	p ˂ 0.001	p ˂ 0.001

TVASS Thirst Visual Analogue Scale Score, HVASS Hunger Visual Analogue Scale Score, T0 30 min before anesthesia induction, T6h 6 h after surgery, T24h 24 h after surgery, SD standard deviation, ES Effect Size

^a Repeated Measures ANOVA; ^b Independent T-test; ^c Bonferroni Statistics

Fig. 4.

The mean and 95% Confidence Interval (CI) of thirst visual analogue scale score (A: TVASS), hunger visual analogue scale score (B: HVASS), nausea visual analogue scale score (C: NVASS), vomiting visual analogue scale score (D: VVASS), pain visual analogue scale score (E: PVASS), and anxiety visual analogue scale score (F: AVASS) in the dextrose and fasting groups at three time points (T0, T6h, and T24h)

Hunger Visual Analogue Scale Score (HVASS)

For HVASS, although no interaction effect was detected (F = 1.31, p = 0.27), both groups improved over time (p < 0.001). The dextrose group exhibited significantly lower scores than the fasting group across all assessments (p < 0.001), with notable improvements from T0 to T24h and T6h to T24h (Table 2; Fig. 4).

Nausea Visual Analogue Scale Score (NVASS)

NVASS showed no significant between-group differences (F = 2.37, p = 0.10). In the fasting group, nausea rose postoperatively (T0–T6h) and later declined (T6h–T24h) (both p < 0.001), while in the dextrose group, changes were not significant. Mean NVASS scores remained within the 1–2.5 range, indicating mild clinical intensity (Table 3; Fig. 4).

Table 3.

Within- and between-group comparisons of the mean NVASSs and VVASSs at three time points

Outcomes			Groups		Between-group comparisonsb
			Fasting (n = 35) mean ± SD	Dextrose (n = 35) mean ± SD
NVASS (0–10)	T0		1.03 ± 1.22	1.43 ± 1.78	p = 0.27
	T6h		2.40 ± 2.42	2.0 ± 2.0	p = 0.45
	T24h		1.34 ± 1.64	1.17 ± 1.15	P = 0.61
	Within-group comparisons (Effect of time)		F = 13.60 ES = 0.28 p = 0.001	F = 7.19 ES = 0.17 p˂0.001	Time-group interactiona
	Pairwise comparisons c	Difference T0 & T6h	p˂0.001	P = 0.216	Mauchly’s Test	Greenhouse ‒ Geisser
		Difference T0 & T24h	P = 0.70	P = 0.99	χ 2 = 12.24 p = 0.002	F = 2.37 ES = 0.03 p = 0.10
		Difference T6h & T24h	p˂0.001	p < 0.001
VVASS (0–10)	T0		1.06 ± 1.23	1.09 ± 0.88	p = 0.91
	T6h		2.83 ± 2.26	3.00 ± 1.91	p = 0.69
	T24h		2.34 ± 2.05	2.09 ± 1.56	P = 0.55
	Within-group comparisons (Effect of time)		F = 17.39 ES = 0.34 p˂0.001	F = 20.37 ES = 0.37 p˂0.001	Time-group interactiona
	Pairwise comparisonsc	Difference T0 & T6h	p˂0.001	p˂0.001	Mauchly’s Test	Sphericity Assumed
		Difference T0 & T24h	p˂0.001	P = 0.008	χ 2 = 0.47 p = 0.79	F = 0.56 ES = 0.008 p = 0.57
		Difference T6h & T24h	P = 0.32	P = 0.007

NVASS Nausea Visual Analogue Scale Score, VVASS Vomiting Visual Analogue Scale Score, T0 30 min before anesthesia induction, T6h 6 h after surgery, T24h 24 h after surgery, SD standard deviation, ES Effect Size

^a Repeated Measures ANOVA; ^b Independent T-test; ^c Bonferroni Statistics

Vomiting Visual Analogue Scale Score (VVASS)

VVASS also revealed no group-level effect (F = 0.56, p = 0.57). In both groups, vomiting increased early postoperatively and declined by T24h (p < 0.001). Mean scores remained within mild ranges [1–3], without statistically significant differences between groups (Table 3; Fig. 4).

Anxiety Visual Analogue Scale Score (AVASS)

Although AVASS did not show a significant interaction (F = 3.12, p = 0.80), both groups improved over time (p < 0.001). The dextrose group had significantly lower anxiety levels at T6h (p = 0.008) and T24h (p = 0.02), suggesting a postoperative anxiolytic effect (Table 4; Fig. 4).

Table 4.

Within- and between-group comparisons of the mean AVASSs and PVASSs at three time points

Outcomes			Groups		Between-group comparisonsb
			Fasting (n = 35) mean ± SD	Dextrose (n = 35) mean ± SD
AVASS (0–10)	T0		4.86 ± 1.78	4.0 ± 2.21	p = 0.08
	T6h		0.94 ± 1.34	0.26 ± 0.61	p = 0.008
	T24h		1.0 ± 1.87	0.23 ± 069	P = 0.02
	Within-group comparisons (Effect of time)		F = 48.69 ES = 0.59 p ˂ 0.001	F = 52.42 ES = 0.61 p ˂ 0.001	Time-group interactiona
	Pairwise comparisons c	Difference T0 & T6h	p ˂ 0.001	p ˂ 0.001	Mauchly’s Test	Greenhouse ‒ Geisser
		Difference T0 & T24h	p ˂ 0.001	p ˂ 0.001	χ 2 = 51.21 p ˂ 0.001	F = 3.12 ES = 0.01 p = 0.8
		Difference T6h & T24h	P = 1.00	P = 1.00
PVASS (0–10)	T0		7.63 ± 2.07	6.06 ± 1.55	p ˂ 0.001
	T6h		8.54 ± 1.86	6.26 ± 2.16	p ˂ 0.001
	T24h		7.66 ± 2.16	4.40 ± 1.92	p ˂ 0.001
	Within-group comparisons (Effect of time)		F = 8.59 ES = 0.204 p ˂ 0.001	F = 30.37 ES = 0.476 p ˂ 0.001	Time-group interactiona
	Pairwise comparisonsc	Difference T0 & T6h	P = 0.03	P = 1.00	Mauchly’s Test	Greenhouse ‒ Geisser
		Difference T0 & T24h	P = 1.00	p ˂ 0.001	χ 2 = 16.66 p ˂ 0.001	F = 6.86 ES = 0.09 P = 0.003
		Difference T6h & T24h	p = 0.001	p ˂ 0.001

AVASS Anxiety Visual Analogue Scale Score, PVASS Pain Visual Analogue Scale Score, T0 30 min before anesthesia induction, T6h 6 h after surgery, T24h 24 h after surgery, SD standard deviation, ES Effect Size

^aRepeated Measures ANOVA; ^b Independent T-test; ^c Bonferroni Statistics

Pain Visual Analogue Scale Score (PVASS)

A significant interaction was found for PVASS (F = 8.86, p = 0.003), with consistently lower pain scores in the dextrose group (p < 0.001). While both groups improved over time (p < 0.001), the dextrose group showed significant reductions from T6h onward, whereas fasting group improvements were less consistent (Table 4; Fig. 4).

In this study, the assumption of sphericity, equal variances of differences between time points, was tested using Mauchly’s test. When violated, Greenhouse-Geisser corrections were applied.

Discussion

Effect of POD intake on perioperative thirst

Our findings indicated that POD intake effectively reduces perioperative thirst, in patients undergoing orthopedic surgery under SA. Several studies support this result, demonstrating that POD intake mitigates thirst across various surgical contexts, including both orthopedic and non-orthopedic surgeries [1, 10, 18, 38, 39]. For instance, Kweon et al. and Akbuğa & Başer reported significant thirst reductions with POC intake [1, 10]. Similarly, patients with Type 2 Diabetes undergoing TKA experienced improved thirst sensations following POC intake, though this improvement was not statistically significant compared to warm water. These findings suggest that both POC and warm water were equally effective in alleviating preoperative thirst [40].

These findings are supported by physiological mechanisms, wherein prolonged fasting depletes glycogen stores, induces a stress response, disrupts plasma osmolarity, and alters glucose metabolism, leading to increased blood glucose and thirst, and exacerbating xerostomia due to preoperative anxiety and medications [1, 11, 41].

Several plausible mechanisms may explain the reduction in thirst following oral carbohydrate or dextrose intake. For example, evidence suggests that POC intake can mitigate psychological factors such as fear and anxiety [26], which in turn reduces sympathetic nervous system activation. This decrease in sympathetic drive improves salivary secretion and helps alleviate dry mouth, thereby diminishing the sensation of thirst [11].

Moreover, antidiuretic hormone (ADH), a key regulator of water-electrolyte and carbohydrate metabolism that is influenced by both plasma osmolarity and non-osmotic factors like blood volume and stress, may be reduced by POC/POD intake [42]. This reduction in ADH levels optimizes plasma osmolarity and attenuates the central neural drive responsible for thirst. Collectively, these mechanisms offer a comprehensive explanation for the improved thirst response observed in patients receiving oral carbohydrates or dextrose compared to those maintained in a fasting state.

In orthopedic patients, diminished gastrointestinal and salivary secretions further compound dehydration, xerostomia, and fatigue, highlighting the importance of POD intake in managing perioperative thirst [1, 11, 41].

However, despite these positive effects, some studies involving diverse surgical populations found no significant differences in postoperative thirst scores between POD intake, placebo, and fasting [21, 43]. These discrepancies may stem from confounding variables such as intraoperative fluid loss, hemorrhage, diuretic use, PACU stay duration, surgery type, and anesthetic agents like opioids and anticholinergics [1, 11, 41]. Further research is necessary to clarify the effect of POD intake on perioperative thirst.

Effect of POD intake on perioperative hunger

While the time-group interaction was insignificant, the results of the t-test indicated that POD intake significantly alleviates perioperative hunger in patients undergoing orthopedic procedures under SA. Over time, the mean hunger score decreased more markedly in the dextrose group compared to the fasting group. Although both groups demonstrated statistically significant reductions in hunger, the clinical impact was more pronounced in the dextrose group, indicating an additional therapeutic benefit of the intervention.

Our findings align with several studies demonstrating the efficacy of POC intake in reducing hunger in different surgical patients [17, 19, 43]. Harsten et al. found that 400 mL of a 12.5% POC solution before total hip arthroplasty (THA) significantly reduced postoperative hunger [44]. Ertural et al. observed that 1200 mL of POC intake significantly lowered hunger scores from day one to five postoperatively [26]. Additional studies further support these findings, highlighting significant reductions in hunger across various orthopedic procedures [10, 40, 45, 46]. POC intake up to two hours before surgery activates anabolic pathways, replenishes glycogen, enhances glucose uptake, and elevates insulin levels, thereby mitigating the catabolic effects of fasting [47, 48].

The observed reduction in hunger sensation following POD administration (2–3 h before surgery) is likely mediated by the coordinated activation of interconnected metabolic and neuroendocrine pathways. Specifically, dextrose ingestion may rapidly elevate blood glucose levels, stimulating insulin secretion from pancreatic β-cells. This insulin surge exerts dual effects: [1] it potentiates leptin release from adipose tissue, which acts via hypothalamic receptors to amplify central satiety signaling [49], and [2] it suppresses ghrelin (hunger hormone) secretion from gastric cells, thereby attenuating peripheral hunger signals [50]. Concurrently, insulin binding within the hypothalamus activates the PI3K/PKB signaling cascade, which may modulate appetite-regulatory neurons through two distinct mechanisms: inhibition of orexigenic neuropeptides (e.g., neuropeptide Y) and potentiation of anorexigenic pathways [48]. These mechanisms may explain the diminished hunger observed in patients receiving dextrose compared to those who were fasting.

Conversely, a meta-analysis of six non-orthopedic studies found no significant reduction in hunger, indicating potential variability due to surgical type, study design, or intervention methods [21]. Despite conflicting evidence, our study highlights the benefits of POD intake in reducing perioperative hunger, necessitating further research to resolve inconsistencies.

Effect of POD intake on perioperative pain

The results of the present study revealed that POD intake significantly mitigates perioperative pain. The findings of some other studies reported substantial reductions exclusively in postoperative pain levels, following POC intake in orthopedic patients [5, 26, 44, 46].

Contrarily, Yap et al. found no notable reduction in postoperative pain among patients undergoing hip fracture surgery [28]. Prolonged fasting raises C-reactive protein (CRP) levels and driving oxidative stress and pain [8]. The POC intake was associated with significantly lower levels of interleukin-6 (IL-6) and CRP, two markers of inflammation contributing to pain. Given that surgical wound pain triggers specific inflammatory and metabolic responses, POC intake might serve as an adjunctive pain-reducing method [5, 17, 26, 44].

In conclusion, the administration of POD significantly improves perioperative pain, potentially enhancing patient satisfaction and expediting recovery [3, 9, 19, 26, 51]. The findings support incorporating POD into preoperative protocols and highlight the need for robust trials to confirm its clinical effectiveness.

Effect of POD intake on perioperative nausea and vomiting

While POD intake showed benefits in reducing thirst, hunger, and pain, its effects on nausea and vomiting are less clear. However, POD intake resulted in clinically significant improvements in nausea scores at both 6 and 24 h post-surgery, as well as better vomiting scores at the 24-hour mark.

Interpreting these outcomes remains complex. In our study, VAS scores for them were low across both groups, with minimal differences between fasting and dextrose groups. This absence of significant perioperative nausea and vomiting complaints suggests that POD intake may not confer additional antiemetic benefits beyond standard fasting protocols. Studies across orthopedic (THA, TKA, hip fracture [HF], proximal femur, osteoporotic fractures) [10, 24, 27, 28, 52–55] and non-orthopedic procedures [6, 17, 23, 39] reported no significant differences in perioperative nausea and vomiting between patients receiving POC (400–1200 mL), plain water, or IV dextrose.

However, some evidence contradicts these findings. Ertural et al. demonstrated that 1200 mL of POC intake significantly reduced postoperative nausea in HA patients [26]. In addition, Harsten et al. reported reduced vomiting scores following 400 mL of POC before THA surgery [44]. The inconsistency in results may reflect variables such as history of PONV, and anesthetic protocols [56–58]. Notably, SA is preferred over general anesthesia for lower limb orthopedic surgery, as SA reduces PONV and opioid use [12, 58–60]. Moreover, preoperative anxiety, a significant predictor of PONV, can activate central dopaminergic pathways, exacerbating nausea and vomiting [56, 61]. Some Studies showed that POC intake reduces anxiety, potentially contributing to lower PONV rates [19, 26, 62]. The present study supports this correlation, with significant anxiety reduction observed in the dextrose group at 6 and 24 h postoperatively, aligning with minimal perioperative nausea and vomiting incidence.

Overall, it can be said that despite these promising findings, ERAS protocols do not explicitly address POC’s role in PONV prevention [47, 56], emphasizing the need for additional research to optimize POD intake strategies for PONV reduction.

Effect of POD intake on perioperative anxiety

The findings revealed that POD intake significantly reduced anxiety at T6h and T24h but showed no statistically significant differences at T0 point. Anxiety reductions at T6h and T24h suggest a postoperative anxiolytic effect, possibly due to attenuated stress responses (e.g., lower cortisol) or faster psychological recovery from reduced discomfort [12, 26, 63]. For instance, POD intake may serve as a metabolic primer by enhancing glucagon-like peptide-1 (GLP-1) secretion via gut-mediated pathways, thereby sustaining postoperative glucose homeostasis and mitigating stress hormones like cortisol, which is directly associated with a reduction in anxiety [64].

Additionally, over time, anxiety scores decreased more in the dextrose group than in the fasting group. Although both groups showed statistically significant reductions, the clinical impact was greater with dextrose, suggesting an added therapeutic benefit.

This aligns with studies demonstrating POC’s capacity to alleviate preoperative anxiety [16, 19, 26]. For instance, Ertural et al. reported sustained anxiety reductions for up to five days post-surgery [26]. In addition, Hausel et al. found similar effects within 40 to 90 min post-intake [16]. Moreover, Shi et al. found that POC intake significantly reduced anxiety scores at 40 and 90 min post-intake in patients [15].

Nonetheless, several studies have reported no significant reduction in anxiety, indicating that POC intake alone may not be sufficient to alleviate the complex psychological stressors experienced during the perioperative period [6, 18].

Preoperative anxiety often stems from prolonged fasting, diagnosis uncertainty, and surgical anticipation, factors that may not be entirely mitigated by carbohydrate intake alone. This combination can lead to silent suffering and difficulty managing symptoms [17, 26, 39, 65]. Given the contradictory results in this area, further investigation is warranted to explore the broader psychological benefits of POC intake in the perioperative stage.

Limitations & future directions 

This study has important limitations. It was conducted in only two hospitals, one public and one private, limiting generalizability to more diverse healthcare settings. Future studies should replicate the intervention across varied geographic and clinical settings to strengthen external validity.

Perioperative IR, a key metabolic indicator, was not assessed. Including IR metrics in future research could provide deeper insights into the physiological effects of POC intake.

The absence of a placebo group and patient blinding restrict causal inference. To distinguish true metabolic effects from placebo responses, future trials should use three-arm designs (fasting, water placebo, and dextrose).

Participant inclusion was limited to ASA I–II, excluding higher-risk patients. Research involving ASA III or IV populations would improve applicability to broader clinical practice.

Finally, while dextrose was used, its comparative effectiveness against other carbohydrates, such as maltodextrin, remains unclear. Trials within orthopedic ERAS protocols, assessing outcomes like mobility and hospital stay, are strongly recommended to refine perioperative strategies.

Conclusion

In patients undergoing orthopedic surgery, POD intake showed no clinically significant improvement in perioperative nausea and vomiting. However, it significantly improved several perioperative parameters, such as reductions in thirst, hunger, anxiety, and pain. Further randomized controlled trials with larger sample sizes are required to validate and expand upon these findings.

Abbreviations

POC

Preoperative Oral Carbohydrate

POD

Preoperative Oral Dextrose

SA

Spinal Anesthesia

VAS

Visual Analogue Scale

PONV

Postoperative Nausea and Vomiting

ASA

American Society of Anesthesiologists

ERAS

Enhanced Recovery After Surgery

IR

Insulin Resistance

PACU

Post-Anesthesia Care Unit

ORIF

Open Reduction and Internal Fixation

TKA

Total Knee Arthroplasty

THA

Total Hip Arthroplasty

TBA

Hip Bipolar Arthroplasty

HF

Hip fracture

TVASS

Thirst Visual Analogue Scale Score

HVASS

Hunger Visual Analogue Scale Score

NVASS

Nausea Visual Analogue Scale Score

VVASS

Vomiting Visual Analogue Scale Score

AVASS

Anxiety Visual Analogue Scale Score

PVASS

Pain Visual Analogue Scale Score

HPA

Hypothalamic–Pituitary–Adrenal Axis

SAM

Sympathetic-Adrenomedullary System

CRH

Corticotropin-releasing hormone

ACTH

Adrenocorticotropic Hormone

IL1β

Interleukin 1 Beta

IL6

Interleukin 6

IL8

Interleukin 8

TNFα

Tumor Necrosis Factorα

CRP

C-Reactive Protein

PI3K

Phosphoinositide 3-Kinase

GLUT4

Glucose Transporter Type 4

SaO2

O2 saturation

NIBP

noninvasive blood pressure

ECG

electrocardiogram

BMI

Body Mass Index

ES

effect size

GLP-1

Glucagon-Like Peptide-1

Author contributions

M.R.Z., M.GH., and M.R. collaborated on the conceptualization and design of this study. M.GH. assumed primary responsibility for data collection, while M.R.Z., MGH, M.R., M.A.S., and A.Y.collectively analyzed and interpreted the dataset. M.R.Z. and M.R. played key roles in drafting and refining the manuscript. All authors thoroughly reviewed and approved the final version of the manuscript for publication.

Funding

This research was financially supported by the Vice Chancellor for Research and Technology at Kashan University of Medical Sciences, as part of a registered project (Registration Number: 402180, dated January 14, 2024).

Data availability

The datasets generated and analyzed during this study are accessible upon reasonable request by contacting the corresponding author.

Declarations

Ethics approval and consent to participate

This study adhered to the ethical standards outlined in the Declaration of Helsinki. Ethical approval was obtained from the ethics committee of Kashan University of Medical Sciences with code IR.KAUMS.NUHEPM.REC.1402.071. Informed written consent was obtained from all participants, who voluntarily enrolled in the study. Participants were informed of their right to withdraw at any stage, and the confidentiality of their personal information was strictly maintained.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.